tests/test-narrow-acl.t

interfaces: introduce and use a protocol class for the `mpatch` module

See f2832de2a46c for details when this was done for the `bdiff` module.

Two things worth pointing out-

  1) The `cffi` module "inherits" the `pure` implementation of `patchedsize()`
     because of its wildcard import.
  2) It's odd that the `mpatchError` lives in both `pure` and `cext` modules.

I initially thought to move the exception into the new class, and make the
existing class name an alias to the class in the new location, but the exception
is created in C code by the `cext` module, so that won't work.  I don't think a
protocol class is approriate, because there's nothing special about the class to
distinguish from any other `Exception`.  Fortunately, nobody is catching this
exception in core, so we can kick the can down the road.

Make a narrow clone then archive it
  $ . "$TESTDIR/narrow-library.sh"

  $ hg init master
  $ cd master

  $ for x in `$TESTDIR/seq.py 3`; do
  >   echo $x > "f$x"
  >   hg add "f$x"
  >   hg commit -m "Add $x"
  > done
  $ cat >> .hg/hgrc << EOF
  > [narrowacl]
  > default.includes=f1 f2
  > EOF
  $ hg serve -a localhost -p $HGPORT1 -d --pid-file=hg.pid
  $ cat hg.pid >> "$DAEMON_PIDS"

  $ cd ..
  $ hg clone http://localhost:$HGPORT1 narrowclone1
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 2 changes to 2 files
  new changesets * (glob)
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

The clone directory should only contain f1 and f2
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  f2

Requirements should contain narrowhg
  $ hg debugrequires -R narrowclone1 | grep narrowhg
  narrowhg-experimental

NarrowHG should track f1 and f2
  $ hg -R narrowclone1 tracked
  I path:f1
  I path:f2

Narrow should not be able to widen to include f3
  $ hg -R narrowclone1 tracked --addinclude f3
  comparing with http://localhost:$HGPORT1/
  searching for changes
  abort: The following includes are not accessible for test: ['path:f3']
  [255]
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  f2
  $ hg -R narrowclone1 tracked
  I path:f1
  I path:f2

Narrow should allow widen to include f2
  $ hg -R narrowclone1 tracked --removeinclude f2 > /dev/null
  $ hg -R narrowclone1 tracked
  I path:f1
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  $ hg -R narrowclone1 tracked --addinclude f2
  comparing with http://localhost:$HGPORT1/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 0 changesets with 1 changes to 1 files
  $ hg -R narrowclone1 tracked
  I path:f1
  I path:f2
  $ ls -A -1 narrowclone1 | sort
  .hg
  f1
  f2